One other thought. If you ultimately decide to make and apply the decals yourself from roll stock, one approach would be to remove the metal trim around the existing decals as they are on the car, and before stripping the decals off, overlay some large brown Kraft paper (like paper grocery bag paper) on top of them, and trace out a pattern of the decal that is underneath. Then you just use the pattern on your new decal material and cut it off the roll to shape.